1. Field
Embodiments of the disclosure relate generally to the field of ducted fan engines and more particularly to embodiments for integral central blading in the fan for secondary air ducting for cooling of components in a reverse flow turbine engine.
2. Background
Ducted fan engines provide high bypass ratios for an efficient propulsion system for air vehicles. By nature, the fan element provides thrust using air displaced through the nacelle or duct surrounding the fan. In most cases, the motive element for the fan, a reciprocating engine or turbojet core is axially aligned with the fan and the fan airflow is directed around the engine or core. Configurations with tractor or pusher style fan/engine integrations may be employed.
Use of a tractor style engine and fan arrangement may be particularly beneficial where integration of the engine and fan in a blended wing body configuration is desired. A turboprop engine provides shaft connection in a tractor arrangement which provides an attractive integrated configuration. However, turboprop engines typically employ a reverse flow arrangement. Use of such reverse flow turbine engines in a ducted fan may result in complex flow arrangements or reduced efficiencies due to the airflow requirements of the engine.
It is therefore desirable to provide a ducted fan having multiple airflow paths to accommodate reverse flow turbine engines or other secondary air requirements in a ducted fan configuration.